Out of the first six numbers of the Fibonacci sequence, four are prime. This limits the possibilities to break down a task equally into smaller tasks to have multiple people work on it in parallel. Doing so could lead to the misconception that the speed of a task could scale proportionally with the number of people working on it. The 2^n series is most vulnerable to such a problem. The Fibonacci sequence in fact forces one to re-estimate the smaller tasks one by one.
